The present invention relates to miniature optical components, such as lenslets and optical components of data communications equipment. More specifically, the present invention relates to a method of manufacturing a three-dimensional structure that may be used as an optical component. However, the present invention has applicability to various other fields requiring the manufacturing of a substrate having minute surface features characterized by intricately shaped side walls.
The increasing demand for high-speed voice and data communications has led to an increased reliance on optical communications, particularly fiber optic communications. The use of optical signals as a vehicle to carry channeled information at high speeds is preferred in many instances to carrying channeled information at other electromagnetic wavelengths/frequencies in media such as microwave transmission lines. Advantages of optical media are, among others, high channel (band-width), greater immunity to electromagnetic interference, and lower propagation loss. In fact, it is common for high-speed optical communications systems to have signal rates in the range of approximately several Gigabits per second (Gbit/sec) to several tens of Gbit/sec.
The above-described recent demand for fiber optic communications is accompanied by a demand for reliable and readily manufacturable optical equipment components for holding an optical waveguide, e.g. an optical fiber(s). Such components may include optical fiber ferrules, and optical switches for selectively coupling optical fibers or the like. The optical fiber ferrule is a commonly utilized component of an optical fiber connector.
FIG. 1 schematically shows an element of a component of optical communications equipment in cross section. Typically, the element will include a holding member 10 defining one or more grooves 11 that constitute a passageway or passageways through the component. The passageway(s) is/are sized to accommodate a waveguide, e.g., an optical fiber(s) 12.
An aspect of the present invention is to provide a method of making a three-dimensional structure having surface features of a predetermined size from a substrate.
A more specific aspect of the present invention is to provide a method of forming one or more grooves in a substrate that can accommodate an optical waveguide. Still further, another more specific aspect of the present invention is to provide a method of forming one or more parabolic or aspherical features in a substrate for use as lenslets.
According to the present invention, a heterogeneous film having a composition that varies in the direction of its thickness is first formed on the substrate. The composition of the film is selected so that the film can be etched at a rate that varies in the direction of its thickness. Useful examples of such thin films are those Silicon oxide and nitrides created by means of the technique known as Chemical Vapor Deposition, in which a precursor-bearing vapor is delivered with other reagents into a hot partial vacuum and/or plasma environment whereupon breakdown and condensation of the vapor upon the substrate results in deposition of the film. By varying the ratios of the constituent precursor and reagent vapors and/or dry gases in situ in the deposition process, a continuum of graded stoichiometry can easily be achieved in such films. This varying of gas ratios may be performed in set steps, each of pre-determined duration, or made continuous at a specified rate of change to control the xe2x80x9cslopexe2x80x9d of the grade in stoichiometry in the z-direction (direction of thickness) of the film. Adjusting the Nitrous oxide to Silane ratio in a typical oxynitride plasma-enhanced chemical vapor deposition process for example, will result in a leanness or richness of Silicon in the film. With a photoresist, or xe2x80x9csoftxe2x80x9d mask deposited on the heterogeneous film, the film is isotropically etched, whereby the film is patterned. Next, the structure comprising the patterned heterogeneous film is etched, during which process the film is eroded, causing increasing amounts of the substrate to become exposed to the etchant throughout the process.
In this way, the pattern of the heterogeneous film is in effect transferred to the substrate. However, the selectivity of the etch process(es) allows the surface features formed in the substrate to have shapes that are different from the shape embodied by the patterned heterogeneous film itself (i.e., a transfer function exists). For example, in one embodiment, relatively shallow openings in the heterogeneous film are used to form deep pits or grooves in the substrate. These deep pits or grooves could be used as channels having the potential, because of their shape, for various uses such as for accommodating optical waveguides. In another embodiment, convex bumps of a given sag are patterned in the heterogeneous film and used to form aspherical or parabolic surface features in the substrate. These surface features could be used as lenslets.